Fill covers are employed in the construction of tanker fluid storage tanks in order to allow filling of the storage tank by a tanker operative, typically by means of a hose attached to a fill arm. Fill covers are traditionally arranged to seal a fill aperture formed in a man-lid, the man-lid typically being a plate removably attached to a man-lid aperture formed in an upper wall of the storage tank. Removal of the man-lid allows improved access to an interior of the tank for maintenance and other operations.
Under UK regulations fill covers for fitting to road vehicles are required to be capable of preventing fluid leakage from a storage tank following a ‘drop test’ involving dropping of the tank from a prescribed height. The test is intended to simulate a sudden increase in pressure of the contents of the storage tank upon a road tanker rolling onto its side. Pressures of up to 126 psi have been recorded for non-pressurised liquid fuels contained within a storage tank of a road tanker under such test conditions.
The problem exists that catastrophic failure of the integrity of a seal between the fill cover and the storage tank can occur due to the sudden increase in pressure resulting in leakage of substantial amounts of fluid from the tank.
US2008/0078127 discloses a remotely actuated manhole system in which a cover is pivotable about a substantially vertical axis with respect to a frame secured with a collar on a bulk carrier. The cover is shiftable vertically between and to locked and unlocked conditions by an inflatable seal member below the cover. The system includes catches that prevent over-rotation of the cover from the open position to the closed position and the catches engage in the locked position by the vertical upward movement of the cover. The inflation of the seal member and the pivoting of the cover are remotely actuated.
EP1717164 discloses a cover and a filler for a tank truck. A fill cover is hingedly coupled directly to a wall of a liquid storage tank of the truck and movable between open and closed conditions.
WO97/42437 discloses a cap unit for a liquid storage tank in which a cap having a skirt is pivotable between open and closed conditions about a vertical axis. The cap and skirt have respective claw-formed catching means adapted to fix the cap in relation to the skirt. The cap has driving means for causing the cap to swing and an inflatable sealing ring mounted in the cap for sealing against the upper surface of the skirt when the cap covers the aperture.